1. Field of the Invention
This invention is directed to an apparatus and methods for spraying fluid in a dual cone spray pattern with high uniformity over a range of fluid flow rates. The apparatus and methods are useful in a variety of technologies including fluid deaeration and purification.
2. Description of the Related Art
In various technologies, fluid is required to be sprayed in a continuous, thin film with a relatively large surface area. For example, to reduce corrosion and increase the useful life of boiler systems and the like, the incoming boiler feedwater is deaerated to remove noncondensable gases such as oxygen and carbon dioxide, that are highly reactive and therefore corrosive, particularly at the elevated operating temperatures present in boiler systems. Deaeration of the feedwater in such boiler systems is thus important to reduce corrosion to extend the useful life of the boiler system. In addition, due to the relatively high pressures and temperatures present in boilers, deaeration can be important for the prevention of a catastrophic failure or rupture of the boiler system and the attendant danger such failure would pose to a person or property in the vicinity of the boiler.
To deaerate the feedwater, before introduction to the boiler system, the feedwater is sprayed into relatively pure steam that is depleted in noncondensable gases. Because the solubility of the noncondensable gases in the feedwater depends on the partial pressure of each gas in the atmosphere surrounding the feedwater, the pure steam draws the noncondensable gases out of the fluid. In addition, the solubility of many noncondensable gases including oxygen and carbon dioxide, is inversely proportional to the temperature, so the heating action of the steam upon the feedwater further causes the feedwater to release dissolved gases. The steam thus deaerates the feedwater by heating and reducing the solubility of the noncondensable gases in the feedwater.
The manner of spraying the feedwater into the steam is an important factor in accomplishing deaeration. The desired spray pattern should be generated from a spray valve in a relatively thin, continuous conical pattern allowing the steam to act uniformly over the maximum possible area of the feedwater spray pattern. Moreover, the spray valve should be capable of generating its spray pattern for a broad range of feedwater flow rates. In addition, the area of the sprayed feedwater pattern should be as large as possible to maximize the area upon which the steam can act to deaerate the sprayed feedwater. Although more than one spray valve can be used to increase the feedwater flow rate into a given space, because the spray patterns of adjacent spray valves will interfere with one another to cause the spray pattern to be nonuniform, there is a limit as to how closely the spray valves can be placed. Also, the use of a greater number of spray valves adds significantly to the deaerator's cost. Therefore, it would be desirable to produce a spray valve and methods that generate a highly uniform spray pattern with an enhanced fluid surface area over a broad range of fluid flow rates, with relatively few parts and thus at a reduced cost, relative to previous spray valves.